(Adds increase in Tuesday auction, reason for low demand)

MEXICO CITY, May 25 (Reuters) - The central bank of Mexico sold just $30 million on Monday at an average price of 15.2659 pesos per dollar in a daily auction of up to $52 million, due to low demand during a U.S. public holiday, the bank said.

It was the first time the bank had sold less than the total on offer at the auction, announced in March, which is aimed at boosting foreign exchange liquidity following a recent slide in the peso currency.

The bank will offer the remaining $22 million not sold on Monday in Tuesday's auction, the bank said via Twitter, in addition to the $52 million regularly offered.

Mexico's foreign exchange commission said Friday it would extend the program, set to expire on June 8, until at least Sept. 29, and could take additional measures to help shield the peso from global volatility.

(Reporting by Alexandra Alper and Jean Luis Arce; Editing by Nick Zieminski)